Battery

Abstract

A battery according to the present disclosure comprises a first electrode, a second electrode, and a solid electrolyte layer that is positioned between the first electrode and the second electrode, wherein: the solid electrolyte layer includes a first solid electrolyte; the first electrode has a base material that is a porous body, and an active material layer that is positioned on the surface of the base material; the active material layer includes Bi; and the first solid electrolyte includes a halide solid electrolyte.

Description

Technical Field

[0001] This disclosure relates to batteries.

Background Art

[0002] In recent years, in lithium secondary batteries that have been actively researched and developed, battery characteristics such as charge-discharge voltage, charge-discharge cycle life characteristics, and storage characteristics are greatly influenced by the electrodes used. Therefore, improvement of battery characteristics has been attempted by improving the electrode active material.

[0003] For example, lithium secondary batteries that use aluminum, silicon, tin, etc. that electrochemically alloy with lithium during charging as electrodes have been proposed for a long time. Patent Document 1 discloses a lithium secondary battery including a negative electrode containing a negative electrode material made of an alloy having silicon, tin, and a transition metal, a positive electrode, and an electrolyte.

[0004] Patent Document 2 discloses a lithium secondary battery including a negative electrode using a silicon thin film provided on a current collector as an active material, a positive electrode, and an electrolyte.

[0005] As a metal that alloys with lithium, bismuth (Bi) can be mentioned. Non-Patent Document 1 discloses a negative electrode made using Bi powder and containing Bi as a negative electrode active material.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0007]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] The present disclosure provides a battery having a structure suitable for improving charge-discharge characteristics.

Means for Solving the Problems

[0009] The battery of the present disclosure includes a first electrode, a second electrode, a solid electrolyte layer positioned between the first electrode and the second electrode, [[ID=二十四]]< >and the solid electrolyte layer includes a first solid electrolyte, the first electrode has a base material that is a porous body, and an active material layer positioned on the surface of the base material, the active material layer contains Bi, the first solid electrolyte includes a halide solid electrolyte.

Effects of the Invention

[0010] According to the present disclosure, a battery having a structure suitable for improving charge-discharge characteristics can be provided. [[ID=四十五]]< >

Brief Description of the Drawings

[0011] [Figure 1] FIG. 1 is a cross-sectional view schematically showing a configuration example of a battery according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a partially enlarged cross-sectional view schematically showing a configuration example of a first electrode in a battery according to an embodiment of the present disclosure. [Figure 3] FIG. 3 is a partially enlarged cross-sectional view schematically showing a modified example of the configuration of a first electrode in a battery according to an embodiment of the present disclosure. [Figure 4]Figure 4 is a graph showing the results of the charge and discharge tests of the test cells according to Examples 1 and 2. [Figure 5] Figure 5 is a graph showing the results of the charge-discharge tests of the test cells related to Reference Examples 1 and 2. [Modes for carrying out the invention]

[0012] (Knowledge that forms the basis of this disclosure) As described in the [Background Technology] section, improvements in lithium secondary batteries are being made to battery characteristics by improving the electrode active material.

[0013] When lithium metal is used as the negative electrode active material, a lithium secondary battery with high energy density per unit weight and per unit volume can be obtained. However, in lithium secondary batteries with this configuration, lithium deposits in a dendrite-like manner during charging. Because some of the deposited lithium metal reacts with the electrolyte, there is a problem of low charge-discharge efficiency and poor cycle characteristics.

[0014] In response to this, the use of carbon, particularly graphite, as the negative electrode has been proposed. In a negative electrode using carbon, charging and discharging occur through the insertion and removal of lithium from the carbon. In a negative electrode with such a configuration, lithium metal does not precipitate in a dendrite-like manner due to the charge-discharge mechanism. Furthermore, in lithium secondary batteries employing a negative electrode with such a configuration, the reaction is topotactic, resulting in excellent reversibility and nearly 100% charge-discharge efficiency. For these reasons, lithium secondary batteries employing negative electrodes made of carbon, particularly graphite, have been put into practical use. However, the theoretical capacity density of graphite is 372 mAh / g, which is about 1 / 10 of the theoretical capacity density of lithium metal, which is 3884 mAh / g. Therefore, the active material capacity density of a negative electrode using graphite is low. Moreover, since the actual capacity density of graphite has almost reached its theoretical capacity density, there is a limit to how high a capacity can be achieved with a negative electrode using graphite.

[0015] In response to these issues, lithium-ion secondary batteries using aluminum, silicon, tin, etc., which electrochemically alloy with lithium during charging, have long been proposed. The capacity density of metals that alloy with lithium is significantly higher than that of graphite. In particular, the theoretical capacity density of silicon is high. Therefore, electrodes using aluminum, silicon, tin, etc., which alloy with lithium, are promising as negative electrodes for batteries exhibiting high capacity, and various secondary batteries using these as negative electrodes have been proposed (Patent Document 1).

[0016] However, negative electrodes using metals that alloy with lithium, as described above, expand when they absorb lithium and contract when they release lithium. When such expansion and contraction are repeated during charging and discharging, the alloy itself, which is the electrode active material, becomes pulverized by charging and discharging, degrading the current collection characteristics of the negative electrode, and thus sufficient cycle characteristics have not been obtained. Several attempts have been made to improve these shortcomings. For example, attempts have been made to deposit silicon on a roughened current collector by sputtering or vapor deposition, or to deposit tin by electroplating (Patent Document 2). In this attempt, the active material, i.e., the metal that alloys with lithium, is in close contact with the current collector as a thin film, so even when the negative electrode repeatedly expands and contracts due to the absorption and release of lithium, the current collection performance hardly deteriorates.

[0017] However, as mentioned above, forming the active material by sputtering or vapor deposition results in high manufacturing costs, making it impractical. Forming the active material by electroplating, which is inexpensive, is more practical, but silicon is extremely difficult to electroplat. Furthermore, tin, which is easily electroplated, has poor discharge flatness, making it unsuitable for use as a battery electrode.

[0018] Another metal that alloys with lithium is bismuth (Bi). Bi forms compounds called LiBi and Li3Bi with lithium (Li). The potentials of LiBi and Li3Bi are almost the same. On the other hand, tin, which has poor discharge flatness, forms several types of compounds with lithium, and the potentials of each compound are quite different from each other. In other words, Bi does not have the property of having a large difference in potential between the multiple types of compounds it forms with lithium, as tin does. For this reason, electrodes containing Bi as an active material have a flat potential and therefore excellent discharge flatness. Consequently, electrodes containing Bi as an active material are considered suitable as electrodes for batteries.

[0019] However, Bi has poor malleability and ductility, making it difficult to manufacture in the form of metal sheets or foils, and the resulting form is small spheres or powder. For this reason, electrodes containing Bi as an active material have been investigated that are manufactured by coating Bi powder onto a current collector. However, electrodes manufactured using such Bi powder have not been able to obtain sufficient cycle characteristics because they become pulverized after repeated charging and discharging, resulting in deterioration of current collection characteristics. For example, Non-Patent Literature 1 describes the manufacture of an electrode containing Bi as an active material using Bi powder and PVdF (polyvinylidene fluoride) or PI (polyimide) as a binder. Non-Patent Literature 1 describes the charging and discharging of a battery manufactured using this electrode. However, the results of the initial charge-discharge curve and cycle characteristics of the manufactured electrode are both very poor. Although measured at a very low rate equivalent to 0.042 IT, the initial charge-discharge efficiency is low and the cycle degradation is severe, so it is not suitable for practical use. Regarding this cyclic degradation, Non-Patent Literature 1 suggests that as the Bi active material expands during Li insertion and contracts during Li desorption, the active material becomes smaller, preventing electron conduction paths from being formed, and thus a decrease in capacity occurs.

[0020] As described above, the inventors focused on Bi, which does not exhibit a large difference in potential between the various compounds formed with Li and has excellent discharge flatness, and diligently investigated batteries that could improve cycle characteristics. As a result, the inventors found that when Bi is formed on the surface of a porous substrate as an active material with the aim of improving the specific surface area of ​​the electrode in contact with the electrolyte, the cycle characteristics of a battery using a solid electrolyte are improved compared to a battery using a liquid electrolyte, and thus completed this disclosure.

[0021] (Summary of one aspect of this disclosure) The battery relating to the first aspect of this disclosure is First electrode and The second electrode and A solid electrolyte layer located between the first electrode and the second electrode, Equipped with, The solid electrolyte layer includes a first solid electrolyte, The first electrode is, A porous substrate, The substrate has an active material layer located on its surface, The active material layer contains Bi, The first solid electrolyte includes a halogenated solid electrolyte.

[0022] When Bi is formed on the surface of a porous substrate as an active material with the aim of improving the specific surface area of ​​the electrode in contact with the electrolyte, the cycle characteristics of a battery using a solid electrolyte are improved compared to a battery using a liquid electrolyte. Thus, the battery according to the first embodiment has a structure suitable for improving charge and discharge characteristics.

[0023] In a second aspect of this disclosure, for example, in the battery according to the first aspect, the active material layer may include elemental Bi.

[0024] The battery according to the second embodiment can have improved charge and discharge characteristics.

[0025] In a third aspect of this disclosure, for example, in a battery according to the first or second aspect, the active material layer may contain Bi as the main component of the active material.

[0026] The battery according to the third embodiment has a higher capacity and improved charge / discharge characteristics.

[0027] In a fourth aspect of this disclosure, for example, in the battery according to the third aspect, the active material layer may substantially consist only of Bi as the active material.

[0028] The battery according to the fourth embodiment has a higher capacity and improved charge / discharge characteristics.

[0029] In a fifth aspect of this disclosure, for example, in a battery according to any one of the first to fourth aspects, the active material layer may include at least one selected from the group consisting of LiBi and Li3Bi.

[0030] The battery according to the fifth embodiment has a higher capacity and improved charge / discharge characteristics.

[0031] In a sixth aspect of this disclosure, for example, in a battery according to any one of the first to fifth aspects, the active material layer may not contain an electrolyte.

[0032] The battery according to the sixth embodiment has a higher capacity and improved charge / discharge characteristics.

[0033] In a seventh aspect of this disclosure, for example, in a battery according to any one of the first to seventh aspects, the substrate may include at least one selected from the group consisting of Cu and Ni.

[0034] The battery according to the seventh embodiment has a higher capacity and improved charge / discharge characteristics.

[0035] In the eighth aspect of this disclosure, for example, in a battery according to any one of the first to seventh aspects, the active material layer may be a plating layer.

[0036] The battery according to the eighth embodiment has a higher capacity and improved charge / discharge characteristics.

[0037] In the ninth aspect of this disclosure, for example, in a battery according to any one of the first to eighth aspects, the halogen solid electrolyte may not substantially contain sulfur.

[0038] The battery according to the ninth embodiment has a higher capacity and improved charge / discharge characteristics.

[0039] In a tenth aspect of this disclosure, for example, in a battery according to any one of the first to ninth aspects, the first solid electrolyte may include a sulfide solid electrolyte.

[0040] The battery according to the tenth embodiment has a higher capacity and improved charge / discharge characteristics.

[0041] In an eleventh aspect of this disclosure, for example, in a battery according to any one of the first to tenth aspects, the first electrode may further include a second solid electrolyte in contact with the active material layer.

[0042] The battery according to the 11th embodiment has a higher capacity and improved charge / discharge characteristics.

[0043] In a twelfth aspect of this disclosure, for example, in a battery according to any one of the first to eleventh aspects, the first electrode may be a negative electrode and the second electrode may be a positive electrode.

[0044] The battery according to the 12th embodiment has a higher capacity and improved charge / discharge characteristics.

[0045] (Embodiments of the present disclosure) Embodiments of this disclosure will be described below with reference to the drawings. The following descriptions are general or specific examples. The numerical values, compositions, shapes, film thicknesses, electrical properties, and secondary battery structures shown below are examples and are not intended to limit this disclosure.

[0046] Figure 1 is a schematic cross-sectional view showing an example of the configuration of a battery 1000 according to an embodiment of this disclosure.

[0047] The battery 1000 comprises a first electrode 101, a second electrode 103, and a solid electrolyte layer 102 located between the first electrode 101 and the second electrode 103. Figure 2 is a schematic partially enlarged cross-sectional view showing an example of the configuration of the first electrode 101 in the battery 1000 according to an embodiment of the present disclosure. As shown in Figure 2, the first electrode 101 has a porous substrate 105 and an active material layer 106 located on the surface of the substrate 105. The active material layer 106 contains Bi. The active material layer 106 contains, for example, Bi alone.

[0048] As shown in Figure 1, the battery 1000 according to this embodiment may further include, for example, a first current collector 100 that is in contact with the first electrode 101. The battery 1000 according to this embodiment may further include, for example, a second current collector 104 that is in contact with the second electrode 103. By providing the first current collector 100 and the second current collector 104, electricity can be extracted from the battery 1000 with high efficiency.

[0049] In the battery 1000, an active material layer 106 containing Bi is formed on the surface of a porous substrate 105 at the first electrode 101. The active material layer 106 is also formed on the inner walls of the pores in the substrate 105, for example, as shown in Figure 2. Therefore, in the battery 1000, the area of ​​the active material layer 106 that can come into contact with the solid electrolyte is larger when the active material layer 106 is formed on the surface of the porous substrate 105 than when it is formed on the surface of a foil-like substrate. Consequently, in the battery 1000, when the same amount of active material is provided on the substrate, the active material layer 106 can be formed thinner than when it is provided on a foil-like substrate. As a result, the load characteristics caused by the solid-phase diffusion of Li ions in the Bi-containing active material layer 106 are improved, for example, the load characteristics during discharge are improved. Therefore, the battery according to this embodiment can improve the charge-discharge characteristics, and in particular, the initial efficiency can be improved. Thus, the battery 1000 according to this embodiment has a structure suitable for improving charge-discharge characteristics.

[0050] In the first electrode 101 shown in Figure 2, the active material layer 106 is formed as a thin film on the inner wall of the pores in the substrate 105, and the pores exist with a relatively high porosity. However, the first electrode 101 is not limited to this configuration. For example, the first electrode 101 may have a structure in which the active material layer 106 almost completely fills the inside of the pores in the substrate 105, resulting in a low porosity. Even if the first electrode 101 has such a structure, the boundary between the substrate 105 and the active material layer 106 can be clearly identified, and it can be said that in the first electrode 101, the substrate 105 is a porous body and the active material layer 106 is formed on the surface of the substrate 105. The active material layer 106 may be formed on a part of the inner wall of multiple pores, or it may be formed on almost the entire surface.

[0051] Battery 1000 is, for example, a lithium secondary battery. The following explanation will use the case where the metal ions intercepted and released in the active material layer 106 of the first electrode 101 and the second electrode 103 during charging and discharging of battery 1000 are lithium ions as an example.

[0052] As described above, the base material 105 is a porous body. In this specification, a porous body means a structure having a plurality of pores, including open pores that open to the outside. Examples of porous bodies in this specification include meshes and porous structures. A porous structure is a structure composed of a porous material having a plurality of pores, and the size of the pores is not particularly limited. An example of a porous structure is a foam. A porous structure may also be a three-dimensional mesh structure in which the pores are in communication with each other. In this specification, "pore" includes both those that are filled with, for example, an active material layer and those that are not. That is, even those that are filled with, for example, an active material layer are considered to be "pores".

[0053] The base material 105 is, for example, conductive. The base material 105 may be formed of a conductive material such as metal, or it may be a porous body made of a non-conductive material such as resin (for example, foamed resin) with a conductive film made of a conductive material provided on its surface. The base material 105 may be, for example, a metal mesh or a porous metal. The base material 105 can function as a current collector for the first electrode 101. That is, if a first current collector 100 is provided, for example, the first current collector 100 and the base material 105 function as current collectors for the first electrode 101. If a first current collector 100 is not provided, for example, the base material 105 functions as a current collector for the first electrode 101.

[0054] The base material 105 may include at least one selected from the group consisting of, for example, Cu and Ni. The base material 105 may be, for example, a metal mesh or a porous metal. The base material 105 may be, for example, a nickel mesh or porous nickel.

[0055] As described above, the active material layer 106 contains Bi. The active material layer 106 may contain Bi as its main component. Here, "the active material layer 106 contains Bi as its main component" is defined as "the Bi content in the active material layer 106 is 50% by mass or more." The Bi content in the active material layer 106 can be determined, for example, by confirming the presence of Bi in the active material layer 106 through elemental analysis by EDX (energy-dispersive X-ray spectroscopy), and then calculating the ratio of the compounds contained by performing Rietveld analysis on the X-ray diffraction results of the active material layer 106.

[0056] With the above configuration, improved charge and discharge characteristics can be obtained.

[0057] The active material layer 106, which mainly contains Bi, may be composed of, for example, a Bi thin film (hereinafter referred to as "Bi thin film").

[0058] The active material layer 106, composed of a Bi thin film, can be fabricated, for example, by electroplating. A method for manufacturing the first electrode 101 by fabricating the active material layer 106 by electroplating is as follows.

[0059] First, the substrate for electroplating is prepared. As the substrate for electroplating, for example, a porous material that can constitute the substrate 105 when the first electrode 101 is formed is used. For example, a metal mesh or a porous metal can be used as the substrate for electroplating. For example, a nickel mesh or porous nickel may be used as the substrate for electroplating. The porous material used as the substrate for electroplating is not particularly limited in structure, as it only needs to be able to constitute the substrate 105 when the first electrode is formed through processes such as electroplating and pressure treatment. It can be appropriately selected according to the desired structure of the first electrode 101. As an example, the porous material used as the substrate for electroplating may be, for example, 0.014 m 2 / cm 3 More than 0.036m 2 / cm 3 It may have the following specific surface areas.

[0060] As an example, nickel mesh is prepared as the substrate for electroplating. After pre-degreasing the nickel mesh with an organic solvent, it is degreased by immersion in an acidic solvent to activate the nickel mesh surface. The activated nickel mesh is connected to a power supply so that current can be applied. The nickel mesh connected to the power supply is immersed in a bismuth plating bath. As a bismuth plating bath, for example, Bi 3+An organic acid bath containing ions and an organic acid is used. Then, by controlling the current density and the application time and applying an electric current to the nickel mesh, Bi is electroplated on the surface of the nickel mesh. After electroplating, the nickel mesh is recovered from the plating bath, the masking is removed, and then it is washed with pure water and dried. By these methods, a Bi plating layer is formed on the surface of the nickel mesh. Note that the bismuth plating bath used for forming the Bi plating layer is not particularly limited and can be appropriately selected from known bismuth plating baths capable of depositing a single Bi thin film. In the bismuth plating bath, as the organic acid bath, an organic sulfonic acid bath, a gluconic acid and ethylenediaminetetraacetic acid (EDTA) bath, or a citric acid and EDTA bath can be used. Further, for example, a sulfuric acid bath may be used in the bismuth plating bath. Further, an additive may be added to the bismuth plating bath.

[0061] Even when, for example, porous nickel is used as the base material for electroplating, a Bi plating layer can be formed by the same method as described above.

[0062] The active material composed of a Bi thin film has, for example, a density of 6.0 g / cm 3 or more and 9.8 g / cm 3 or less. The density of the active material composed of a Bi thin film may be 6.5 g / cm 3 or more and 9.8 g / cm 3 or less, or may be 7.0 g / cm 3 or more and 9.8 g / cm 3 or less. Note that the density of the active material composed of a Bi thin film can be obtained, for example, by calculating using the Archimedes' method. As an example, when the active material layer 106 is substantially composed of a thin film made of an active material, at least a part of the thin film is taken out as a sample, and the density of the sample is calculated using, for example, the Archimedes' method, whereby the density of the active material can be obtained.

[0063] The following describes in more detail the configuration of the battery 1000 of this embodiment, using the case where the first electrode 101 is the negative electrode and the second electrode 103 is the positive electrode as an example.

[0064] [First electrode] As described above, the first electrode 101 has a porous substrate 105 and an active material layer 106 located on the surface of the substrate 105. The configuration of the substrate 105 and the active material layer 106 is as described above, but will be explained in more detail below.

[0065] The first electrode 101 functions as a negative electrode. Therefore, the active material layer 106 contains a negative electrode active material that has the property of intercalating and releasing lithium ions. The active material layer 106 contains Bi, which functions as the negative electrode active material.

[0066] Bi is a metallic element that alloys with lithium. When Bi functions as the negative electrode active material, lithium is intercalated during charging by Bi forming an alloy with lithium. That is, in the active material layer 106, a lithium-bismuth alloy is formed when the battery 1000 is charged. The formed lithium-bismuth alloy includes, for example, at least one selected from the group consisting of LiBi and Li3Bi. That is, when the battery 1000 is charged, the active material layer 106 includes, for example, at least one selected from the group consisting of LiBi and Li3Bi. When the battery 1000 is discharged, lithium is released from the lithium-bismuth alloy, and the lithium-bismuth alloy returns to Bi.

[0067] Bi, as the negative electrode active material, reacts during charging and discharging of the battery 1000, for example, as follows. Note that the following example of reaction is for the case where the lithium bismuth alloy produced during charging is Li3Bi. Charging: Bi+3Li + +3e - →Li3Bi Discharge: Li3Bi→Bi+3Li + +3e -

[0068] The active material layer 106 may contain substantially only Bi as the active material. In this case, the battery 1000 can have improved capacity and improved cycle characteristics. Note that "the active material layer 106 contains substantially only Bi as the active material" means, for example, that the amount of other active materials besides Bi in the active material layer 106 is 1% by mass or less. The active material layer 106 may contain only Bi as the active material.

[0069] The active material layer 106 does not necessarily contain an electrolyte. For example, the active material layer 106 may be a layer made of Bi and / or a lithium bismuth alloy produced during charging. The electrolyte referred to here is a liquid or solid electrolyte having lithium ion conductivity.

[0070] The active material layer 106 may be disposed in direct contact with the surface of the substrate 105. Furthermore, if the battery 1000 includes a first current collector 100, the substrate 105 may be disposed in contact with the first current collector 100.

[0071] The active material layer 106 may be in the form of a thin film.

[0072] The active material layer 106 may be a plating layer. The active material layer 106 may be a plating layer provided in direct contact with the surface of the substrate 105. That is, as described above, the active material layer 106 may be a Bi plating layer formed on the surface of the substrate 105.

[0073] If the active material layer 106 is a plating layer provided in direct contact with the surface of the substrate 105, the active material layer 106 adheres firmly to the substrate 105. This further suppresses the deterioration of the current collection characteristics of the first electrode 101 that occurs when the active material layer 106 repeatedly expands and contracts. Therefore, the charge and discharge characteristics of the battery 1000 are further improved. Furthermore, if the active material layer 106 is a plating layer, the active material layer 106 contains a high density of Bi, which alloys with lithium, thus enabling even higher capacity.

[0074] The active material layer 106 may contain materials other than Bi or Bi-containing alloys. The Bi-containing alloys referred to here are, for example, lithium bismuth alloys produced by charging reactions (e.g., LiBi and Li3Bi).

[0075] The active material layer 106 may further contain a conductive material.

[0076] Examples of conductive materials include carbon materials, metals, inorganic compounds, and conductive polymers. Examples of carbon materials include graphite, acetylene black, carbon black, Ketjenblack, carbon whiskers, needle coke, and carbon fibers. Examples of graphite include natural graphite and artificial graphite. Examples of natural graphite include lump graphite and flake graphite. Examples of metals include copper, nickel, aluminum, silver, and gold. Examples of inorganic compounds include tungsten carbide, titanium carbide, tantalum carbide, molybdenum carbide, titanium boride, and titanium nitride. These materials may be used individually or in combination.

[0077] The active material layer 106 may further contain a binder.

[0078] Examples of binders include fluororesins, thermoplastics, ethylene propylene diene monomer (EPDM) rubber, sulfonated EPDM rubber, and natural butyl rubber (NBR). Examples of fluororesins include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), and fluororubber. Examples of thermoplastics include polypropylene and polyethylene. These materials may be used individually or in combination.

[0079] The thickness of the active material layer 106 is not particularly limited and may be, for example, 0.1 μm or more and 100 μm or less.

[0080] The material of the base material 105 is, for example, a single metal or alloy. More specifically, it may be a single metal or alloy containing at least one selected from the group consisting of copper, chromium, nickel, titanium, platinum, gold, aluminum, tungsten, iron, and molybdenum. The base material 105 may also be stainless steel.

[0081] The base material 105 may include at least one selected from the group consisting of copper (Cu) and nickel (Ni).

[0082] The structure of the base material 105 is as described above. The base material 105 may be considered as the current collector of the first electrode 101 or as part of the current collector.

[0083] The thickness of the first electrode 101 may be 10 μm or more and 2000 μm or less. That is, the overall thickness of the porous substrate 105, on which the active material layer 106 is provided on the surface, may be 10 μm or more and 2000 μm or less. Having such a thickness for the first electrode 101 allows the battery to operate at high output.

[0084] Figure 3 is a schematic partially enlarged cross-sectional view showing a modified configuration of the first electrode in a battery according to an embodiment of this disclosure. As shown in the modified configuration in Figure 3, the first electrode 101 may further include a second solid electrolyte 107 in contact with the active material layer 106. For example, the second solid electrolyte 107 may be contained within the pores of the substrate 105. Therefore, in the battery 1000, the area of ​​the active material layer 106 that can come into contact with the active material and the solid electrolyte is larger when the active material layer 106 is formed on the surface of the porous substrate 105 than when it is formed on the surface of a foil-shaped substrate. Consequently, in the battery 1000, when the same amount of active material is provided on the substrate, the active material layer 106 can be formed thinner than when it is provided on a foil-shaped substrate. As a result, the load characteristics caused by the solid-phase diffusion of Li ions in the active material layer 106 containing Bi are improved, for example, the load characteristics during discharge are improved. Therefore, by having the first electrode in this configuration, the battery according to this embodiment can further improve the charge-discharge characteristics.

[0085] In the first electrode 101 shown in Figure 3, the active material layer 106 is formed as a thin film on the inner wall of the pores in the substrate 105, and the region inside the active material layer 106 is almost completely filled with the second solid electrolyte 107. Thus, the first electrode 101 may have a low porosity, with the inside of the pores in the substrate 105 almost completely filled with the active material layer 106 and the second solid electrolyte 107. Even if the first electrode 101 has such a structure, the boundary between the substrate 105 and the active material layer 106 can be clearly identified, and it can be said that in the first electrode 101, the substrate 105 is a porous body and the active material layer 106 is formed on the surface of the substrate 105. The active material layer 106 may be formed on a part of the inner wall of a plurality of pores, or it may be formed on almost the entire surface.

[0086] The second solid electrolyte 107 may include a halide solid electrolyte, which is substantially sulfur-free. Here, in this specification, a halide solid electrolyte means a solid electrolyte containing a halogen element. The halide solid electrolyte may contain oxygen in addition to a halogen element. The halide solid electrolyte does not contain sulfur (S).

[0087] The second solid electrolyte 107 may contain a sulfide solid electrolyte. Here, in this specification, a sulfide solid electrolyte means a solid electrolyte containing sulfur (S). The sulfide solid electrolyte may contain not only sulfur but also halogen elements.

[0088] The second solid electrolyte 107 may contain an oxide solid electrolyte, a polymer solid electrolyte, or a complex hydride solid electrolyte.

[0089] Examples of halogenated solid electrolytes, sulfide solid electrolytes, oxide solid electrolytes, polymer solid electrolytes, and complex hydride solid electrolytes that can be used in the second solid electrolyte 107 are the same as the examples of halogenated solid electrolytes, sulfide solid electrolytes, oxide solid electrolytes, polymer solid electrolytes, and complex hydride solid electrolytes that can be used in the first solid electrolyte contained in the solid electrolyte layer 102, as described later.

[0090] [First current collector] In the battery 1000 according to this embodiment, the first current collector 100 may or may not be provided. The first current collector 100 may be provided in contact with the first electrode 101, for example. The first current collector 100 may be provided in contact with the base material 105 of the first electrode 101, for example. By providing the first current collector 100, electricity can be extracted from the battery 1000 with high efficiency.

[0091] The material of the first current collector 100 is, for example, a single metal or alloy. More specifically, it may be a single metal or alloy containing at least one selected from the group consisting of copper, chromium, nickel, titanium, platinum, gold, aluminum, tungsten, iron, and molybdenum. The first current collector 100 may also be stainless steel.

[0092] The first current collector 100 may include at least one selected from the group consisting of copper (Cu) and nickel (Ni).

[0093] The first current collector 100 may be in the form of a plate or foil. From the viewpoint of easily ensuring high conductivity, the first current collector 100 may be a metal foil. The thickness of the first current collector 100 may be, for example, 5 μm or more and 20 μm or less.

[0094] The first current collector 100 may be a laminated film.

[0095] [Solid electrolyte layer] As the first solid electrolyte contained in the solid electrolyte layer 102, a halogen solid electrolyte, a sulfide solid electrolyte, an oxide solid electrolyte, a polymer solid electrolyte, or a complex hydride solid electrolyte may be used.

[0096] The first solid electrolyte may include a halide solid electrolyte.

[0097] The halide solid electrolyte may be, for example, a material represented by the following compositional formula (1). Li α M β X γ ...Equation (1) Here, α, β, and γ are values ​​greater than 0, M is at least one selected from the group consisting of metal elements and metalloid elements other than Li, and X is at least one selected from the group consisting of F, Cl, Br, and I.

[0098] "Metallic elements" are B, Si, Ge, As, Sb, and Te.

[0099] "Metallic elements" refer to all elements in groups 1 through 12 of the periodic table, excluding hydrogen, as well as all elements in groups 13 through 16, excluding B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se. In other words, they are the elements that can form cations when combined with halogen elements to create inorganic compounds.

[0100] In compositional formula (1), M may contain Y, and X may contain Cl and Br.

[0101] As the halide solid electrolyte, for example, Li3(Ca, Y, Gd)X6, Li2MgX4, Li2FeX4, Li(Al, Ga, In)X4, Li3(Al, Ga, In)X6, LiI, etc. may be used. Here, in these solid electrolytes, the element X is at least one selected from the group consisting of F, Cl, Br, and I. In the present disclosure, when an element in a formula is represented as "(Al, Ga, In)", this notation indicates at least one element selected from the group of elements within the parentheses. That is, "(Al, Ga, In)" is synonymous with "at least one selected from the group consisting of Al, Ga, and In". The same applies to other elements.

[0102] Another example of the halide solid electrolyte is Li a Me b Y c a compound represented by X6. Here, a + mb + 3c = 6 and c > 0 are satisfied. Me is at least one selected from the group consisting of metal elements and metalloid elements other than Li and Y. m represents the valence of Me. "Metalloid element" means B, Si, Ge, As, Sb, and Te. "Metal element" means all elements included in Groups 1 to 12 of the periodic table (excluding hydrogen), and all elements included in Groups 13 to 16 of the periodic table (excluding B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se).

[0103] To enhance the ionic conductivity of the halide solid electrolyte material, Me may be at least one selected from the group consisting of Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Zr, Hf, Ti, Sn, Ta, and Nb. The halide solid electrolyte may be Li3YCl6, Li3YBr6, or Li3YBr p Cl 6-p where p satisfies 0 < p < 6.

[0104] The first solid electrolyte may include a sulfide solid electrolyte.

[0105] Examples of sulfide solid electrolytes include Li2S-P2S5, Li2S-SiS2, Li2S-B2S3, Li2S-GeS2, Li 3.25 Ge 0.25 P 0.75 S4, or Li 10 GeP2S 12 These may be used.

[0106] Examples of oxide solid electrolytes include NASICON-type solid electrolytes represented by LiTi2(PO4)3 and its elemental substitutions, (LaLi)TiO3-based perovskite-type solid electrolytes, and Li 14 ZnGe4O 16 , LiSICON-type solid electrolytes such as Li4SiO4, LiGeO4 and their elemental substitutions, Li7La3Zr2O 12 Garnet-type solid electrolytes, such as those represented by elemental substitutions thereof, Li3PO4 and its N-substituted counterparts, and glass or glass ceramics based on Li-BO compounds such as LiBO2 and Li3BO3, with Li2SO4, Li2CO3, etc., added, can be used.

[0107] As a polymer solid electrolyte, for example, a compound of a polymer compound and a lithium salt can be used. The polymer compound may have an ethylene oxide structure. Polymer compounds having an ethylene oxide structure can contain a large amount of lithium salt. Therefore, the ionic conductivity can be further increased. Examples of lithium salts that can be used include LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), and LiC(SO2CF3)3. One lithium salt selected from the exemplified lithium salts can be used alone. Alternatively, a mixture of two or more lithium salts selected from the exemplified lithium salts can be used.

[0108] Examples of complex hydride solid electrolytes that can be used include LiBH4-LiI and LiBH4-P2S5.

[0109] The solid electrolyte layer 102 may contain a halide solid electrolyte. The halide solid electrolyte does not contain sulfur.

[0110] The solid electrolyte layer 102 may consist substantially of a halide solid electrolyte. In this specification, "substantially" means that the inclusion of impurities at a content of less than 0.1% is permitted. The solid electrolyte layer 102 may consist solely of a halide solid electrolyte.

[0111] With the above configuration, the ionic conductivity of the solid electrolyte layer 102 can be increased. This reduces the decrease in the battery's energy density.

[0112] The solid electrolyte layer 102 may further contain a binder. The same material that can be used for the active material layer 106 may be used as the binder.

[0113] The solid electrolyte layer 102 may have a thickness of 1 μm or more and 500 μm or less. If the solid electrolyte layer 102 has a thickness of 1 μm or more, the first electrode 101 and the second electrode 103 are less likely to short-circuit. If the solid electrolyte layer 102 has a thickness of 500 μm or less, the battery can operate at high power.

[0114] The shape of the solid electrolyte is not particularly limited. If the solid electrolyte is a powder material, its shape may be, for example, needle-shaped, spherical, ellipsoidal, etc. For example, the solid electrolyte may be particulate.

[0115] For example, if the solid electrolyte is particulate (e.g., spherical), the median diameter of the solid electrolyte may be 100 μm or less, or 10 μm or less.

[0116] In this disclosure, “median diameter” means the particle size at which the cumulative volume in the volume-based particle size distribution is equal to 50%. The volume-based particle size distribution is measured, for example, by a laser diffraction analyzer or an image analyzer.

[0117] The solid electrolyte contained in the solid electrolyte layer 102 can be manufactured by the following method.

[0118] The raw material powder is prepared to have the desired composition. Examples of raw material powders include oxides, hydroxides, halides, or acid halides.

[0119] For example, if the target composition is Li3YBr4Cl2, LiBr, YCl, and YBr are mixed in a molar ratio of approximately 3:0.66:0.33. The raw material powders may also be mixed in a pre-adjusted molar ratio to compensate for any compositional changes that may occur during the synthesis process.

[0120] The raw material powders are reacted with each other mechanochemically (i.e., using the mechanochemical milling method) in a mixing device such as a planetary ball mill to obtain a reactant. The reactant may be calcined in a vacuum or an inert atmosphere. Alternatively, a mixture of raw material powders may be calcined in a vacuum or an inert atmosphere to obtain the reactant. Calcination is preferably carried out at a temperature of 100°C or higher and 300°C or lower for at least one hour. To suppress compositional changes during calcination, it is preferable that the raw material powders be calcined in a sealed container such as a quartz tube.

[0121] These methods yield the solid electrolyte for the solid electrolyte layer 102.

[0122] [Second electrode] The second electrode 103 functions as the positive electrode. The second electrode 103 contains a material capable of intercalating and releasing metal ions such as lithium ions. This material is, for example, the positive electrode active material.

[0123] The second electrode 103 includes a positive electrode active material. If the battery 1000 according to this embodiment includes a second current collector 104, the second electrode 103 is disposed, for example, between the second current collector 104 and the solid electrolyte layer 102.

[0124] The second electrode 103 may be positioned on the surface of the second current collector 104, in direct contact with the second current collector 104.

[0125] As positive electrode active materials, for example, lithium-containing transition metal oxides, transition metal fluorides, polyanionic materials, fluorinated polyanionic materials, transition metal sulfides, transition metal oxysulfides, or transition metal oxynitrides can be used. An example of a lithium-containing transition metal oxide is LiNi 1-x-y Co x Al y O2((x+y)<1), LiNi 1-x-y Co x Mn y Examples include O2((x+y)<1) or LiCoO2. In particular, when a lithium-containing transition metal oxide is used as the positive electrode active material, the manufacturing cost of the electrode can be reduced and the average discharge voltage of the battery can be increased. For example, the positive electrode active material may also contain Li(Ni,Co,Mn)O2.

[0126] The second electrode 103 may contain a solid electrolyte. As the solid electrolyte, the solid electrolyte exemplified as the material constituting the solid electrolyte layer 102 may be used.

[0127] The positive electrode active material may have a median diameter of 0.1 μm or more and 100 μm or less. When the positive electrode active material has a median diameter of 0.1 μm or more, the positive electrode active material and the solid electrolyte can form a good dispersion state. This improves the charge and discharge characteristics of the battery. When the positive electrode active material has a median diameter of 100 μm or less, the lithium diffusion rate improves. This allows the battery to operate at high power.

[0128] The positive electrode active material may have a larger median diameter than the solid electrolyte. This allows the positive electrode active material and the solid electrolyte to form a good dispersion state.

[0129] From the viewpoint of the battery's energy density and output, the ratio of the volume of the positive electrode active material to the sum of the volume of the positive electrode active material and the volume of the solid electrolyte in the second electrode 103 may be 0.30 or more and 0.95 or less.

[0130] To prevent the solid electrolyte from reacting with the positive electrode active material, a coating layer may be formed on the surface of the positive electrode active material. This can suppress the rise in the reaction overpotential of the battery. Examples of coating materials included in the coating layer are sulfide solid electrolytes, oxide solid electrolytes, or halide solid electrolytes.

[0131] The thickness of the second electrode 103 may be 10 μm or more and 500 μm or less. When the thickness of the second electrode 103 is 10 μm or more, a sufficient energy density of the battery can be ensured. When the thickness of the second electrode 103 is 500 μm or less, the battery can operate at high power.

[0132] The second electrode 103 may contain a conductive material for the purpose of enhancing electronic conductivity.

[0133] The second electrode 103 may contain a binder.

[0134] The same materials that can be used for the active material layer 106 may be used as the conductive material and binder.

[0135] The second electrode 103 may contain a non-aqueous electrolyte, a gel electrolyte, or an ionic liquid in order to facilitate the transfer of lithium ions and improve the output characteristics of the battery.

[0136] Non-aqueous electrolytes include a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent. Examples of non-aqueous solvents are cyclic carbonate solvents, linear carbonate solvents, cyclic ether solvents, linear ether solvents, cyclic ester solvents, linear ester solvents, or fluorine solvents. Examples of cyclic carbonate solvents are ethylene carbonate, propylene carbonate, or butylene carbonate. Examples of linear carbonate solvents are dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate. Examples of cyclic ether solvents are tetrahydrofuran, 1,4-dioxane, or 1,3-dioxolane. Examples of linear ether solvents are 1,2-dimethoxyethane, or 1,2-diethoxyethane. An example of a cyclic ester solvent is γ-butyrolactone. An example of a linear ester solvent is methyl acetate. Examples of fluorinated solvents include fluoroethylene carbonate, methyl fluoropropionate, fluorobenzene, fluoroethyl methyl carbonate, or fluorodimethylene carbonate. One non-aqueous solvent selected from these may be used alone, or a mixture of two or more non-aqueous solvents selected from these may be used.

[0137] Examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), or LiC(SO2CF3)3. One lithium salt selected from these may be used alone, or a mixture of two or more lithium salts selected from these may be used. The concentration of the lithium salt is, for example, in the range of 0.5 mol / liter to 2 mol / liter.

[0138] As the gel electrolyte, polymer materials impregnated with a non-aqueous electrolyte can be used. Examples of polymer materials include polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, or polymers having ethylene oxide bonds.

[0139] Examples of cations contained in ionic liquids are: (i) aliphatic chain quaternary salts such as tetraalkylammonium or tetraalkylphosphonium, (ii) Aliphatic cyclic ammonium compounds such as pyrrolidiniums, morpholiniums, imidazoliniums, tetrahydropyrimidiniums, piperadiniums, or piperidiniums, (iii) Nitrogen-containing heterocyclic aromatic cations such as pyridiniums or imidazoliums That is the case.

[0140] An example of anion contained in an ionic liquid is PF6. - BF4 - SbF6 - AsF6 - , SO3CF3 - , N(SO2CF3)2 - , N(SO2C2F5)2 - , N(SO2CF3)(SO2C4F9) - , or C(SO2CF3)3 - That is the case.

[0141] The ionic liquid may contain a lithium salt.

[0142] In the above description, an example configuration was explained in which the first electrode 101 is the negative electrode and the second electrode 103 is the positive electrode. However, the first electrode 101 may also be the positive electrode and the second electrode 103 may be the negative electrode.

[0143] When the first electrode 101 is the positive electrode and the second electrode 103 is the negative electrode, the active material layer 106 is the positive electrode active material layer. That is, the Bi contained in the active material layer 106 functions as the positive electrode active material. In this case, the second electrode 103, which is the negative electrode, is made of, for example, lithium metal.

[0144] [Second current collector] In the battery 1000 according to this embodiment, the second current collector 104 may or may not be provided. The second current collector 104 is provided, for example, in contact with the second electrode 103. By providing the second current collector 104, electricity can be extracted from the battery 1000 with high efficiency.

[0145] The material of the second current collector 104 is, for example, a single metal or alloy. More specifically, it may be a single metal or alloy containing at least one selected from the group consisting of copper, chromium, nickel, titanium, platinum, gold, aluminum, tungsten, iron, and molybdenum. The second current collector 104 may be stainless steel.

[0146] The second current collector 104 may contain nickel (Ni).

[0147] The second current collector 104 may be in the form of a plate or foil. From the viewpoint of easily ensuring high conductivity, the second current collector 104 may be a metal foil. The thickness of the second current collector 104 may be, for example, 5 μm or more and 20 μm or less.

[0148] The second current collector 104 may be a laminated film.

[0149] The battery 1000 has a basic configuration of a first electrode 101, a solid electrolyte layer 102, and a second electrode 103, and is sealed in a sealed container to prevent the ingress of air and moisture. The shape of the battery 1000 can be coin-shaped, cylindrical, prismatic, sheet-shaped, button-shaped, flat, or stacked. [Examples]

[0150] The details of this disclosure are disclosed below with reference to examples and reference examples. The following examples are illustrative and this disclosure is not limited to the following examples.

[0151] (Example 1) <Fabrication of the first electrode> As a pretreatment, a nickel mesh (10cm x 10cm, thickness: 50μm, manufactured by Niraco Co., Ltd., "NI-318200") was pre-degreased with an organic solvent, and then degreased by immersion in an acidic solvent to activate the nickel mesh surface. In 1.0 mol / L of methanesulfonic acid, bismuth methanesulfonate was added as a soluble bismuth salt. 3+ A plating bath was prepared by adding ions to a concentration of 0.18 mol / L. The activated nickel mesh was connected to a power supply so that current could be applied, and then immersed in the plating bath. Subsequently, the current density was set to 2 A / dm². 2 By controlling the process, Bi was electroplated onto the nickel mesh surface to a thickness of approximately 5 μm. After electroplating, the nickel mesh was recovered from the acidic bath, washed with pure water, and dried. The amount of Bi plated onto the nickel mesh was 1.032 g.

[0152] <Preparation of solid electrolytes> In an argon atmosphere with a dew point of -60°C or lower (hereinafter referred to as a "dry argon atmosphere"), LiBr, YCl3, and YBr3 were prepared as raw material powders in a molar ratio of LiBr:YCl3:YBr3 = 3:2 / 3:1 / 3. These raw material powders were ground and mixed in a mortar to obtain a mixed powder. Next, the obtained mixture of raw material powders was calcined in an electric furnace in a dry argon atmosphere at 500°C for 3 hours to obtain a calcined product. The obtained calcined product was ground in a mortar using a pestle. In this way, a solid electrolyte having the composition Li3YBr4Cl2 was obtained.

[0153] <Preparation of test cells> A first electrode was used as the working electrode within an insulating outer cylinder having an inner diameter of 9.4 mm. A solid electrolyte, Li3YBr4Cl2 (80 mg), was laminated on the working electrode, and then an indium-lithium alloy (molar ratio In:Li = 1:1) (200 mg) was laminated as the counter electrode to obtain a laminate. The indium-lithium alloy was produced by pressing small pieces of lithium foil onto indium foil and diffusing lithium into the indium. A pressure of 360 MPa was applied to this laminate to form the working electrode, solid electrolyte layer, and counter electrode. In the laminate, the thickness of the first electrode (working electrode) was 65 μm, the thickness of the solid electrolyte layer was 400 μm, and the thickness of the counter electrode was 15 μm.

[0154] Next, a current collector made of stainless steel was attached to the working electrode and the counter electrode, and a current collector lead was attached to the current collector.

[0155] Finally, an insulating ferrule was used to isolate the inside of the insulating outer cylinder from the outside atmosphere, thereby sealing the inside of the cylinder.

[0156] As described above, a test cell of Example 1 was obtained, in which an electrode obtained by forming an active material layer made of Bi on a nickel mesh (i.e., the first electrode) was used as the working electrode, and a lithium-indium alloy was used as the counter electrode. The test cell fabricated here is a unipolar test cell using a working electrode and a counter electrode, and is used to test the performance of one electrode in a secondary battery. Specifically, the electrode under test is used as the working electrode, and a suitable amount of active material sufficient to support the reaction of the working electrode is used as the counter electrode. Since this test cell tests the performance of the first electrode as a negative electrode, a large excess of lithium-indium alloy was used as the counter electrode, as is commonly done. A negative electrode whose performance has been tested using such a test cell can be used as a secondary battery by combining it with a positive electrode containing a positive electrode active material, such as a transition metal oxide containing Li, as described in the above embodiment.

[0157] <Charge-discharge cycle test> The fabricated test cell underwent charge-discharge testing under the following conditions. Assuming a Bi theoretical capacity of 384 mAh / g from the electroplated Bi mass, the cell was charged to 0V (0.62V vs. Li+ / Li) at a constant current value where the rate was 0.1 IT relative to Bi, and then discharged to 1.38V (2.0V vs. Li+ / Li). The charge-discharge test of the test cell was performed in a constant temperature bath at 25°C. Figure 4 is a graph showing the results of the charge-discharge test of the test cell according to Example 1. The test cell according to Example 1 maintained its initial discharge capacity even after 50 charge-discharge cycles.

[0158] (Example 2) <Fabrication of the first electrode> As a pretreatment, porous nickel (10cm x 10cm, thickness: 1.6mm, manufactured by Niraco Co., Ltd., "NI-318161") was pre-degreased with an organic solvent, and then degreased by immersion in an acidic solvent to activate the surface of the porous nickel. In 1.0 mol / L of methanesulfonic acid, bismuth methanesulfonate was added as a soluble bismuth salt. 3+ A plating bath was prepared by adding ions to a concentration of 0.18 mol / L. The activated porous nickel was connected to a power supply so that an electric current could be applied, and then immersed in the plating bath. Subsequently, the current density was set to 2 A / dm². 2 By controlling the process, Bi was electroplated onto the porous nickel surface to a thickness of approximately 5 μm. After electroplating, the porous nickel was recovered from the acidic bath, washed with pure water, and dried. The amount of Bi plated onto the porous nickel was 0.526 g.

[0159] <Preparation of solid electrolytes> A solid electrolyte having the composition Li3YBr4Cl2 was prepared by the same method as in Example 1.

[0160] <Preparation of test cells> As the first electrode, the first electrode of Example 2 was used, which had a configuration in which an active material layer 106 made of Bi was provided on a substrate 105 made of porous nickel. Except for this point, the test cell of Example 2 was obtained in the same manner as the test cell of Example 1. The thickness of the first electrode, which is the working electrode, was 400 μm, the thickness of the solid electrolyte layer was 400 μm, and the thickness of the counter electrode was 15 μm.

[0161] <Charge-discharge cycle test> A charge-discharge test was performed on the test cell of Example 2, which was fabricated under the same conditions as in Example 1. Figure 4 is a graph showing the results of the charge-discharge test of the test cell of Example 2. The test cell of Example 2 maintained its initial discharge capacity even after 50 charge-discharge cycles.

[0162] (Reference example 1) <Fabrication of the first electrode> As a pretreatment, a nickel mesh (10cm x 10cm, thickness: 50μm, manufactured by Niraco Co., Ltd., "NI-318200") was pre-degreased with an organic solvent, and then degreased by immersion in an acidic solvent to activate the nickel mesh surface. In 1.0 mol / L of methanesulfonic acid, bismuth methanesulfonate was added as a soluble bismuth salt. 3+ A plating bath was prepared by adding ions to a concentration of 0.18 mol / L. The activated nickel mesh was connected to a power supply so that current could be applied, and then immersed in the plating bath. Subsequently, the current density was set to 2 A / dm². 2 By controlling the process, Bi was electroplated onto the nickel mesh surface to a thickness of approximately 5 μm. After electroplating, the nickel mesh was recovered from the acidic bath, washed with pure water, and dried. The amount of Bi plated onto the nickel mesh was 1.032 g. The plated nickel mesh was punched out to 2 cm x 2 cm to prepare the first electrode.

[0163] <Preparation of test cells> The first electrode was used as the working electrode. A 0.34 μm thick piece of Li metal was used as the counter electrode. The Li metal was double-coated with a microporous separator (Cellguard 3401, manufactured by Asahi Kasei). As the electrolyte, a solution was prepared by dissolving LiPF6 in vinylene carbonate (VC) at a concentration of 1.0 mol / L. In this way, the test cell of Reference Example 1 was obtained.

[0164] <Charge-discharge cycle test> The test cell of Reference Example 1 was charged to 0V (vsLi+ / Li) with a constant current of 2mA, and then discharged to 2.0V (vsLi+ / Li). This was considered one cycle, and the charge-discharge cycle test was performed for 21 cycles. The battery was tested in a constant temperature chamber at 25°C. Figure 5 is a graph showing the results of the charge-discharge test of the test cell related to Reference Example 1. The discharge capacity of the test cell of Reference Example 1 decreased to less than 20% of the initial discharge capacity after 20 charge-discharge cycles.

[0165] (Reference example 2) <Fabrication of the first electrode> As a pretreatment, porous nickel (10cm x 10cm, thickness: 1.6mm, manufactured by Niraco Co., Ltd., "NI-318161") was pre-degreased with an organic solvent, and then degreased by immersion in an acidic solvent to activate the surface of the porous nickel. In 1.0 mol / L of methanesulfonic acid, bismuth methanesulfonate was added as a soluble bismuth salt. 3+ A plating bath was prepared by adding ions to a concentration of 0.18 mol / L. The activated porous nickel was connected to a power supply so that an electric current could be applied, and then immersed in the plating bath. Subsequently, the current density was set to 2 A / dm². 2 By controlling the process, Bi was electroplated onto the porous nickel surface to a thickness of approximately 5 μm. After electroplating, the porous nickel was recovered from the acidic bath, washed with pure water, and dried. The amount of Bi plated onto the porous nickel was 0.526 g. The plated porous nickel was punched out to a 2 cm x 2 cm rectangle to prepare the first electrode.

[0166] <Preparation of test cells> The first electrode was used as the working electrode. A 0.34 μm thick piece of Li metal was used as the counter electrode. The Li metal was double-coated with a microporous separator (Cellguard 3401, manufactured by Asahi Kasei). As the electrolyte, a solution was prepared by dissolving LiPF6 in vinylene carbonate (VC) at a concentration of 1.0 mol / L. In this way, the test cell of Reference Example 2 was obtained.

[0167] <Charge-discharge cycle test> The test cell of Reference Example 2 was charged to 0V (vsLi+ / Li) with a constant current of 10mA, and then discharged to 2.0V (vsLi+ / Li). This was considered one cycle, and the charge-discharge cycle test was performed for up to 50 cycles. The battery was tested in a constant temperature chamber at 25°C. Figure 5 is a graph showing the results of the charge-discharge test of the test cell related to Reference Example 2. The discharge capacity of the test cell of Reference Example 1 decreased to less than 20% of its initial discharge capacity after 20 charge-discharge cycles.

[0168] From the above results, it can be seen that a battery using a porous material as a substrate and combining an electrode containing Bi as an active material with a solid electrolyte exhibits a higher discharge capacity retention rate in charge-discharge cycle tests compared to a battery using a liquid electrolyte. In other words, the battery of this disclosure, which comprises a porous substrate, a first electrode containing a Bi-containing active material layer located on the surface of the substrate, and a solid electrolyte layer, has been confirmed to have a structure suitable for improving charge-discharge cycle characteristics.

[0169] In the examples described herein, a halide solid electrolyte Li3YBr4Cl2 was used as the solid electrolyte, but similar effects can be expected with other common solid electrolytes. [Industrial applicability]

[0170] The battery described herein can be used, for example, as an all-solid-state lithium secondary battery. [Explanation of symbols]

[0171] 1000 batteries 100 First collector 101 First Electrode 102 Solid electrolyte layer 103 Second Electrode 104 Second collector 105 Substrate 106 Living Matter Layer 107 Second Solid Electrolyte

Claims

1. First electrode and The second electrode and A solid electrolyte layer located between the first electrode and the second electrode, Equipped with, The solid electrolyte layer includes a first solid electrolyte, The first electrode is, A porous substrate, The substrate has an active material layer located on its surface, The active material layer contains Bi, The first solid electrolyte includes a halogen solid electrolyte, The first electrode is a negative electrode, The second electrode is the positive electrode. Lithium-ion rechargeable battery.

2. The active material layer contains Bi elemental, The lithium secondary battery according to claim 1.

3. The active material layer contains Bi as the main component of the active material. The lithium secondary battery according to claim 1.

4. In the active material contained in the active material layer, the amount of other active materials besides Bi is 1% by mass or less. The lithium secondary battery according to claim 3.

5. The active material layer consists of LiBi and Li 3 Includes at least one selected from the group consisting of Bi, The lithium secondary battery according to claim 1.

6. The active material layer does not contain electrolytes. The lithium secondary battery according to claim 1.

7. The substrate comprises at least one selected from the group consisting of Cu and Ni. The lithium secondary battery according to claim 1.

8. The active material layer is a plating layer. The lithium secondary battery according to claim 1.

9. The halogenated solid electrolyte is sulfur-free. The lithium secondary battery according to claim 1.

10. The first solid electrolyte includes a sulfide solid electrolyte. The lithium secondary battery according to claim 1.

11. The first electrode further includes a second solid electrolyte in contact with the active material layer. The lithium secondary battery according to claim 1.

12. The density of the active material is 6.0 g / cm³ or more and 9.8 g / cm³ or less. The lithium secondary battery according to claim 3.

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